This invention relates to enclosures of the type used in industrial electrical and hydraulic systems and the like, and more particularly to an improved fastener for attaching removable access panels in such enclosures.
Control components, wiring, and plumbing in industrial electrical and hydraulic control systems are often mounted in cabinet-like enclosures. Such enclosures typically include a frame having a flange for attachment of one or more removable access panels. Each access panel typically includes a number of quick-release fasteners installed through holes in the panel for attaching the panel to the flange.
Such quick-release fasteners typically include a retaining screw having a shaft section defining an axis. One end of the retaining screw is formed into a head having a larger outer diameter than the shaft of the screw, and including a slot, recess, flats, or knurling so that the screw may be installed and removed by hand or with common hand tools. The opposite panel retaining end of the screw is typically formed to provide male or female screw threads, an L-shaped form, or some other type of quick-attach retainer profile, cooperating with the flange or a mating thread, etc., attached to the flange for securing the access panel to the frame of the enclosure.
The fastener also typically includes a bushing having an outer profile which includes a first section shaped for insertion through a hole in the panel, a shoulder for positioning the bushing in the panel, and a bore extending through the bushing about the axis to receive the shaft with the head of the retaining screw adjacent the shoulder on the outside of the panel, and the opposite panel retaining end on the inside of the panel. The bushing is typically secured within the hole by a C-ring which snaps into a groove of the bushing inside of the panel after the bushing is inserted through the hole. It is common in such fasteners to have the head and panel retaining inner end of the retaining screw larger in diameter than the bore of the bushing, or otherwise configured such that the screw is held captive within the bushing.
In some fasteners, a spring is also provided between the head of the screw and the shoulder of the bushing to facilitate installation and removal of the panel by pulling the panel retaining end of the screw away from the flange after disengagement.
Inherent problems associated with the manufacture and use of prior art quick-release fasteners of the type described above increase the initial and life cycle cost of the fasteners and enclosures in which they are used. Performance and aesthetic desirability of the enclosures is also reduced by the inherent problems associated with the use of the prior art fasteners.
Using C-rings for retaining the fastener in the access panel creates several problems. The initial labor and part cost is increased by the need to stock, handle, and install the separate C-ring. The risk of dropping a C-ring into the enclosure during installation, operation, or maintenance activities is undesirable. There is also an aesthetic problem, in that unless the C-rings clamp the bushing of the fastener tightly against both faces of the panel, the fasteners may rattle when the panel is removed, giving a customer the impression of sloppy workmanship and shoddy design. To alleviate this problem, the bushings can be closely matched to a given panel thickness, but where several different panel thicknesses are used by a manufacturer, perhaps even on the same enclosure, this requires a different fastener configuration for each panel thickness.
Prior quick-release fasteners of the type described above having a head and panel retaining end configured to be larger in diameter or otherwise shaped so as to not slide through the bore of the bushing of the completed fastener are difficult to manufacture. Because neither the head nor panel retaining end of the retaining screw will fit through the bushing, the bushing must be installed on the shaft section of the retaining screw during manufacture prior to forming the head or forming the panel retaining end of the retaining screw. Where the fastener must ultimately be plated, or where a spring is utilized between the head and shoulder of the bushing, the necessity of installing the bushing midway through formation of the screw is highly undesirable.
It is an object of my invention, therefore, to provide an improved enclosure through the use of an improved quick-release fastener for access panels of the enclosure. Other objects of my invention include providing:
(1) a fastener that is more readily manufactured than prior fasteners at a lower cost;
(2) a fastener that is self-retaining;
(3) a fastener that is self-retaining in panels of several different thicknesses;
(4) a fastener in which the component parts can be separately manufactured and subsequently assembled following completion of all manufacturing operations on the various component parts;
(5) a bushing which can be installed on the shaft section of a retaining screw of a fastener following completion of all manufacturing steps for the retaining screw; and
(6) a fastener which can be retrofitted into existing panel and enclosure designs to improve their desirability.
My invention provides such an improved enclosure and solves the problems defined above through the use of an improved quick-release fastener. According to one aspect of the invention, the improved quick-release fastener includes a bushing having an outer profile including a first section shaped for insertion through a hole in an access panel of an enclosure, a shoulder and a resilient tang axially spaced from the shoulder for retaining the bushing in the panel, and a bore extending through the bushing about an axis for receiving a shaft section of a retaining screw of the quick-release fastener. In preferred embodiments of this aspect of my invention, the tang includes a serrated surface configured to bear against an inner surface of the access panel, with the serrations having notches shaped for receipt of the inner surface of panels of several thicknesses. According to another aspect of my invention, the improved quick-release fastener utilizes a bushing comprised of two segments separable along a plane passing through the axis of the bore of the bushing. In preferred embodiments, the two segments include corresponding male and female alignment formations for aligning the bushing about the bore. In a highly preferred embodiment, the two segments of the bushing are identical.
Other aspects and advantages of my invention will be apparent from a review of the following drawings and detailed description of exemplary embodiments.